<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // class Father {
        //     constructor() {

        //     }
        //     money() {
        //         console.log(100);
        //     }
        // }
        // class Son extends Father {

        // }
        // var son = new Son();
        // son.money();

        class Father {
            constructor(x, y) {
                this.x = x;
                this.y = y;
            }
            sum() {
                console.log(this.x * this.y);
            }
        }
        class Son extends Father {
            constructor(x, y) {
                // this.x = x;
                // this.y = y;
                super(x, y);
            }
        }
        var son = new Son(1, 2);
        son.sum();
    </script>
</body>

</html>